Controlled engine exhaust gas recirculation (“EGR”) is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A known EGR system employs an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the induction fuel-air flow entering the engine for combustion so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen.
It is known to mount an EGR valve on an engine manifold where the valve is subjected to a harsh operating environment that includes wide temperature extremes and vibrations. Stringent demands are imposed by governmental regulation of exhaust emissions that have created a need for improved control of such valves. Use of an electric actuator is one means for obtaining improved control, but in order to be commercially successful, such an actuator must be able to operate properly in such extreme environments for an extended period of usage. Moreover, in mass-production automotive vehicle applications, component cost-effectiveness and size may be significant considerations.
A known EGR valve typically relies on a valve that is actuated by a movement of a valve stem by an electromagnetic actuator. The EGR valve is typically mounted to a manifold or a housing that has one port exposed to exhaust gases and another port exposed to an intake manifold of the engine. Under certain operating conditions, the valve abuts a valve seat surface so as to prevent exhaust gases from flowing into the intake manifold. Depending on the operating conditions, the valve can be moved away from the seat to permit a controlled amount of exhaust gases into the intake manifold.
An EGR valve having a linear actuator including a rotary motor, which possesses more accurate, quicker and generally linear responses can be advantageous by providing improved control of tailpipe emissions, improved driveability, and/or improved fuel economy for a vehicle having an internal combustion engine that is equipped with an EGR system.
Further, an EGR valve having a linear actuator including a rotary motor, which is more compact in size while delivering the same or an increased magnitude of force over the travel of the valve stroke can be advantageous because of limitations on available space in a vehicle engine compartment. Thus, it would be advantageous to provide for an EGR valve that is compact yet powerful enough to deliver a generally constant force over an extended stroke distance.